It takes at least two months for the follow-up letter to my GP to arrive after any specialist appointment at my local hospital even if a change in medication is involved. It makes me think of the one time custom of putting the older veg. to the front of the stall each day with the new at the back so that nobody ever got fresh if you follow my drift. The backlogs seem to be accepted as normal.. If you were older,, they would most probably rely on the clinical assessment and dx. of PD as the more likely but they need to be doubly sureat your age I was left to draw my own conclusion from the fact that the "probably" which preceded "idiosyncratic (means cause unknown) Parkinsons" in the first GP letter had disappeared by the next letter my having responded well to the meds. i.e. if you respond to the PD drug its PD. By the way you might want to bear in mind that frozen shoulder often precedes by a couple of years the onset of obvious Parkinsons symptoms.
Its a good thing you have found this site as on diagnosis 60% of PD patients receive no information whatsoever according to a survey by PD UK. All their publications are excellent and very clear. If you join PD UK - I think its still only £4 p.a.- you get a whole bunch of leaflets etc. Helpline above can help with welfare, employment as well as medical issues. When I was dx six years ago, I was left in limbo for six months and the Helpline was a godsend. Most GP's will admit they know little about Parkinsons
Hope you get some answers soon